Inorganic electroluminescent elements have been so far used as, for example, panel-type light sources of back light and the like. However, a high AC voltage is required to drive the luminescent elements. Recently, organic electroluminescent elements (organic EL elements) using organic materials as luminescent materials have been developed [Appl. Phys. Lett., 51, 913 (1987)]. The organic electroluminescent element is an element having a structure that a thin film containing a compound having a luminescent performance is held between an anode and a cathode, in which electrons and holes are injected in the thin film for recombination to generate excitons and luminescence occurs using light released in deactivating the excitons. The organic electroluminescent element enables luminescence at a low DC voltage of several volts to several tens of volts. Further, luminescence of various colors (for example, red, blue and green) is possible by selecting types of fluorescent organic compounds. The organic electroluminescent element having such characteristics is expected to be applied to various luminescent elements, display devices and the like. However, a luminescent brightness is generally low, which is unsatisfactory in practice.
As a method for improving a luminescent brightness, an organic electroluminescent element using, for example, tris(8-quinolinolato)aluminum as a host compound and coumalin derivatives or pyran derivatives as a guest compound (dopant) in a luminescent layer is proposed [J. Appl. Phys., 65, 3610 (1989)]. Further, an organic electroluminescent element using anthracene derivatives as a material of a luminescent layer is proposed (Japanese Patent Laid-Open Nos. 12,600/1996 and 111,458/1999). Still further, an organic electroluminescent element using anthracene derivatives as a guest compound of a luminescent layer is proposed (Japanese Patent Laid-Open Nos. 36,832/1998 and 294,179/1998).
However, these luminescent elements are not said either to have a satisfactory luminescent brightness and a satisfactory luminescent life.
Organic electroluminescent elements that allow luminescence with a higher luminescent brightness and a longer life have been currently in demand.